Despite continued improvement in the technical aspects of cardiopulmonary bypass procedures, a majority of cardiac surgical patients demonstrate postoperative cognitive deficits and three percent actually suffer frank strokes. Although it is not yet proven, the majority of researchers believe that these deficits are caused by emboli.In order to directly correlate the occurrence of neurologic and neuropsychologic deficits with intraoperative cerebral embolic events, it is essentialto be able to measure the occurrence of emboli traveling toward the brain.The applicants have proposed to develop a practical, cost effective instrument which would be able to intraoperatively monitor emboli. To achieve this goal, they have proposed to design a specialized ultrasonic detector which would have a very large effective field of view. Dedicated hardware will be designed that will be capable of analyzing the reflected power level and the audio frequency spectrum needed to count and characterize the emboli. Digital filtering and anti-coincidence techniques will be applied to eliminate the effects of spurious signals. Software will be developed to allow the rapid andaccurate analysis of embolic events under clinical conditions. A clinical prototype will be fabricated and used to study cardiac surgery patients at the Bowman Gray School of Medicine. By this approach, the measuring probe could be positioned against the patient and continuously monitor the emboli count without the constant attention of a skilled operator.